The overall objective of this project is to understand the mechanisms which lead to the synthesis of highly specific antibody molecules, the nature of genes which influence and control immune responses, and the regulation of gene expression during lymphoid cell differentiation. We are attempting to define by combined immunological and chemical approaches the structural differences between genetically controlled polymorphic forms of rabbit immunoglobulins (immunoglobulin allotypes) and between classes, subclasses, types and subtypes of their polypeptide chains. We utilize such information in a variety of studies including breeding experiments, studies of the factors which influence phenotypic expression of alleles or chain types, and studies of membrane-associated markers.